I will not lie, I am less than blown away. Or rather, blown away in the wrong direction. I get this is a dev build, but there’s some things that are just “really?”
Starting off with the quite frankly, crap texture quality. None of the vehicles have any shine to them without HQ reflections turned on, which I usually don’t for performance reasons.
Speaking of performance, this is the part that really was disappointing. I heard, and expected that 0.4.8 was going to have improved performance by quite a bit. I got the exact opposite, getting about half or a third of the framerate I did in 0.4.7. On Bajarama, with the 2WD Gavril Zeta, I got about 23 frames per second. (I get that my computer is less than suited for Rigs of Rods, but still). In this version, I get about 12, and it looks substantially worse due to the “matte finish” on everything.
The icing on the cake is that this version broke 0.4.7.
Is it possible I did something wrong? Of course. It is possible that I goofed up something, and that broke the textures, so maybe this criticism is invalid, which I wouldn’t be at all surprised if I did due to 4.7 not working, but as it stands now, this was a letdown.
As a preface let me start by saying these are Development Builds. They are not fully polished releases and no one should expect them to be, it is a privilege, not your right that the devs even release these builds for users to try new features. So you need to take a few steps back from your entitled attitude.
The "crap texture quality" is not an issue with textures, but shaders. The migration to Ogre 1.11 is still a work in progress, and the issues you're describing were caused by the incomplete migration of Caelum sky. This issue is fixed in the latest dev builds.
As far as performance, part of the solution lies in your post, turn off HQ reflections, it's obvious your PC can't handle them. To further track down any performance issues, load a map and spawn a physics intensive car, get in the car and take note of your FPS, then pause the physics with J. If your FPS increases at all that means your FPS is being limited by your CPU. You may be able to help this a little bit by adjusting the "NumWorkerThreads" setting in your RoR.cfg file. The default setting will be "=0", assuming you have a quad core CPU you'd probably want to set it to 3, which would use 3 of your 4 available threads.
Now for the "broken" 0.4.7. The 0.4.8 dev build and 0.4.7 have slightly different options within the configurator, meaning their config files can't be shared by both versions. So if you want to use 0.4.7 or vice versa, you have to delete RoR.cfg and let the configurator generate a new file.
Again, issues are to be expected with development releases. If you don't want to experience new issues then it's best to leave testing to users who can deal with them and help further development by aiding the devs in finding solutions, or even just report them properly instead of whining on the forum.