more lens advice - Telephoto mirror or refractive ?

[Monkey boy 1]

Don't want to tread on the other 'Lens advice' thread so here is mine.

I have a Canon EOS 1000D and have a few lenses with it, the largest being a 300mm consina telephoto. Now I would like to get a better telephoto, but have not got megga money to spend.
I have seen some mirror telephoto lenses and want to know that is the difference / advantage / disadvantages of the mirror lens over the usual refractive lenses, apart from the size.
To me, the mirror lens looks like a cheaper option, which is fine for me at the moment, but just want your take on this type of lens before I commit.

Any info is much appreciated.

Thanks

[RobDickinson]

Advantages - cheap reach.

Disadvantages - slow, no autofocus, dodgy bokeh, no zoom, lowish IQ.

TBH get a 150-600 sigma/tamron.

[Simpo Two]

Pro: Cheap range, compact size
Con: Fixed aperture, usually f8 (though not so much of a problem in these high-ISO days).

Out of focus specular highlights become rings, which may or may not bother you.