The main issue is performance. You can take a look at the RSAC Performance Page which explains what is known about this.
The bottom line is that each request-scope bean takes around 10 microseconds to contruct, which while it isn't terribly much, can mount up after a while if you have enough of them. This was the only reason RSAC was made - it's around 100x faster than Spring at constructing beans, although a bit less flexible.
In general if the performance becomes an issue, you can use the RSACBridgeProxy to bridge a request-scope dependency to application scope and so move your producers back again.
Although I'm a bit suspicious as to why your producers are needing to depend on things in request scope - in general if you want them to access bits of the bean model this should either i) be persistent and so not request-scope, or ii) issued by means of EL bindings. Could you give me some idea of what you are doing?