This is usual the result of software companies prioritizing the development of new features over software quality, and is has little to do with supporting multiple platforms.
Don't be quick to criticize the Lightroom developers, you are basing your opinion on two invalid assumptions.
I do share your opinion that Lightroom is inexcusably slow, but I was happy to discover that 40% of Lightroom's code was written in Lua. The use of interpreted languages can greatly increase programmer productivity and reduce the number of bugs, in the long term this is a good thing for users.
Lightroom's performance problems are mostly the result of poor memory management. I have noticed that Lightroom's memory usage will unexpectedly balloon for no apparent reason. (If it means anything to you, I suspect the culprit may be a poorly designed garbage collection system.)
Thanks for the response:
I accept that my "possible" explanations may be wrong, not knowing for sure.
Since this is a photography forum, I guess we shouldn't get too technical. But we are users and like others who commented here, I couldn't care less if one or another language is used, provided that our experience is not unacceptably degraded. Most of us working on a "normal" but "not beefed up machine" think LR's speed IS a problem (when I buy a PC, I choose a fast but not top of the line machine and then keep it for 5 or 6 years, only upgrading subsystems like HD, memory,etc.. when needs arise. My next is for Vista, but not before at least one year).
My multiplatform hypothesis is an observation, not a demonstration. I did not aim to discredit Lua or interpreted languages whatsoever. Moreover, I agree that there could be ways to make multiplatform software as fast on all platform (FrameMaker, that Adobe acquired many years ago, is such software). But I have observed that the shortcuts (compromises) often made in crossplatform software DO cost performance. Probably that the effort to NOT compromise are deemed unecessary, assuming folks will upgrade their machines sooner or later.
Anyway, I did not intend to create an argument. Regardless of the multiplatform development'relevance to this discussion I would simply point out that it might be a sort of wishful thought that LR's speed improve dramatically in the short term since it is probably resulting from design choices that would be hard to fix. Owning a version of the software, I can only hope to be proven wrong, but when I look at other Adobe software, I can tell that performance, minimal memory usage etc. is really not something Adobe spends a lot of effort fine tuning.