Since this question has been linked to, it may be worth an update. This bike is still "being upgraded", as I really like it, the upgrades list is now:
Almost systematic replacements (= I expect to do them with every bike):
- saddle, grips, pedals, tires
- I also fitted "inner bar ends" (Sqlab 411), to have one additional hand position.
- Cassette: 11/42 10-speed (I kept the original 46/30 crank and FD).
- Rear Derailleur: RD-M5120
- Shifters: Deore M4100 (rear) & M5100 (front)
The goal here was to increase range on the low side, and have a Deore instead of an Acera. The difference in shifting performance is noticeable, especially over time, as the Acera quickly developed some play. The Deore is still as sharp as in the beginning. The front shifter was not necessary, but is a "one lever" one, which is the way to go on 2x transmissions.
- Wheels: Mavic Allroad UST + quality tubeless tires (Michelin Power Gravel for summer, Pirelli Cinturato Gravel M for winter)
The stock ones were unserviceable (the cones bearings were worn out, and it was not possible to find replacements). The key here was to take hubs with modular designs - not unique to Mavic, that being said. These wheels feature different kinds of end-caps (so can potentially be reused on a "real" gravel bike if I decide to purchase one - the dual sport uses Quick Release, gravel bikes use thru-axles), and user-replaceable free-hubs bodies. Also, user-replaceable free-hub bodies opens the possibility to use XD(R) or Microspline if I were to change the transmission again - but it's not foreseen in the near future. As Armand stated, it's surprising to see the difference a good wheelset makes - this one is 1kg lighter, and inside rim width was increased by 6mm. It also remained more true than the previous, despite more abuses.
- Seatpost: Canyon VCLS 2.0 (then replaced by a Bontrager Carbon)
Carbon seatposts are great upgrades: they bring a bit of compliance to aluminium frames for a "reasonable" cost (the VCLS 2.0 costs 200€, but by bringing compliance, it avoided the purchase of a new bike). On long rides, it makes the difference (for me at least) between back pain and no back pain - even with the Bontrager, that is not as compliant as the VCLS. I had to replace the VCLS 2.0 because it was too short, as the frame of the Dual Sport is quite slanted, but I really like this seatpost - I moved it to another bike.
- Suspension fork: Rockshox Paragon Gold
Replacement because the previous was worn. I could try an air suspension in the meantime, considered was worth to pay the extra (and also 900g lighter...)
I also had some rattling issues, mostly attributable to an un-fastened rear brake hydraulic hose (internally routed). I had to find a solution to silence the frame (I installed zip-ties around the hose, and pushed them in the frame).
I'll answer to some arguments given in the answers (or elsewhere):
- Cost: it is often stated than upgrading a bike is more expensive than selling the bike and buying a new one. In my case, all upgrades were combined with the replacement of worn parts, so the cost of the upgrade is the difference between the replacement and the upgraded part, not the sticker price of the upgraded component. I also only used mid-range components, that are reasonably priced. So yes, at this stage, the total upgrades cost has maybe exceed what I would have paid for an upper version of this range, but not by much, and the chosen components are better suited to my criteria and use than what I would have gotten with any "stock bike". Note that I did the upgrades myself (so didn't had to count labour), and could benefit from discounts when purchasing components. It is also often stated that the manufacturers can purchase components in bulk, and so have better costs, but this argument is for me not always valid, as they also tend to increase their margin with the price.
- Upgrading to a gravel bike: debatable, but for me not worth the cost — I still prefer flat handle bars with an alternative hand position. There are some specs for my use that cannot be found on gravel bikes (close to 600% range, front suspension with enough travel). I would consider a gravel if I were to replace this bike though.
That being said, there are reasons to not go for the upgrade:
- time consuming: choosing the right combinations took some time. Some of it could have been "outsourced" to a bike mechanics, but then the cost would have risen by a margin.
- going for a more specialized bike: these hybrids are often chosen by people who don't know what they want exactly, as first bikes. I live in a place that is generally bike friendly (Belgium), and with a good network of secondary roads with rough surfaces (cobblestones or heavy gravel). This compromise makes perfect sense here, but not necessarily elsewhere, where a dedicated road bike and a MTB would make more sense.