The DF-02 is an entry level four wheel drive kit. Its quite a good value kit , it comes with oil dampers and ball bearings for the prop shaft and diffs to begin with, so the only immediate upgrades to consider are eight 1150 bearings for the front knuckles and rear hubs. I've not had any issue with the plastic propshaft but I only run the kit 540 silver can motor (27T). For hotter motors its advisable to use a TT01 aluminum prop shaft to replace the kit plastic prop shaft. You could go crazy with extra hopups such as the DF02 turnbuckle kit, aluminum steering rack, and aluminum dampers, but then you're approaching the cost of a more capable DB01. I think it's best to do keep the kit as is for a first timer, then ball rcae the hubs for a little more speed (less resistance) and as the motor gets uprated then do the propshaft.
Ground clearance isn't quite as good as some of the other buggies, but going for standard size buggy tires and wheels instead of the kit tires and wheels helps some. The large diameter (2.2") wheels that go on the DF03 Dark Impact are perfect for this. Pro-Line Dirt Hawgs last quite a while on mixed surface use, much better than spikes on concrete/tarmac
This is a very durable platform perfect for bashing. The motor pinion, diff pinions, diff ring gears, and diff spider gears are all metal and hardly wear. Weak points include the front shock tower and possibly the suspension arm mounts molded into the main chassis tub. My son has the Rising Storm - he broke the front shock tower with a front corner hit against a kerb, but uprating to alloy towers front and rear sorted that issue; he's never cracked a suspension mount although you could fill the hollowed out areas to possibly improve the strength.
Its a good looking buggy with reliable drivetrain.
If I were buying now I'd also look at the new TT-02B Neo Scorcher - its very similar to the DF-02 but based ont he latest TT-02 chassis. There are a few 'concerns' about plastic diff gears on the Neo Scorcher/TT-02 but as yet its people commenting during the build process rather than failures in service. The good news is parts are cheap, in line with kit pricing and these are easy to work on.
My son's Rising Storm , with alloy towers..
Wheels now replaced with 2.2 disc wheels and mini pin tyres, ground clearance improves about 1/4"