I've played MotoGP 13 a lot more and really like it but it comes with some major niggles that Milestone can't seem to remove from their sims:
The AI in the PC version needs reworking as they wobbly through the corners and are jet powered down straights. Not only does the AI bash and crash into your rider like he (or she) is not there, they are capable of braking the lap record from a standing start just like the realistic level AI found in SBK games. Riding in Grand Prix mode with pro physics and realistic AI, Lorenzo beat the lap record at Mugello on the opening lap whilst Pedrosa beat the Phillip Island record from a standing start. It's not like an experienced player can't match the speed of the AI however as MotoGP 13 is considered a sim, it's laughable to be able to get close to any lap records from a standing start. At the start of the career mode which consists of 4 Moto3 wildcard rides, I was consistently faster than the AI in qualifying yet was stuggling to keep with the top riders in the races.
Why can't I start a race in first gear Milestone? This was an issue in the SBK series and appears in MotoGP 13 too. The AI make rocket starts whilst the player is forced to mash the change gear button in the hope first gear is selcted at the right time.
Weather effects are laughably bad. If you've played pCARS or any of the Codemasters F1 games, you'll know how great in-game weather can look. MotoGP 13 features the cardboard cut-out version; no rain drops or spray on either visor or camera yet the track has puddles and refective surfaces. I'm saddened to report that SBK '08 has better weather effects. Grip levels and lap times aren't overly effected by the rain either. Other issues are the multiplayer works intermittently at present, commentary is limited to a few lines prior to each session and at the end of every race, pop-up is noticable at every track and visual representation of damage is terrible and very limited. The lap counter can get stuck in all modes, resulting in a never ending race if a player selects 100% race length.
Milestone are compiling a list of issues to fix on the PC which is all very well but it begs the question of how much QA testing was undertaken prior to release. It's not as if the console versions are devoid of issues either; Alan Bioston from VVV Automotive mentioned in his Le Mans video that the Xbox version has major framerate issues. Anyone with the Xbox version ride around Indy and you'll have some of the worst framerates seen on the console.
Despite all of the above, I am enjoying the career mode and the overall experience however I believe unless you are a motorcycling enthusiast I'd avoid MotoGP 13 until a patch is released or a price drop/Steam sale. Alternatively, think about buying GP Bikes.
YouTube video - MotoGP 13 vs GP Bikes