presence speakers are they worth it?

anyone with presence speakers care to share their experience? 

I'd say it depends on the speakers used. Although they won't be dealing with as much as the front LCR's, ideally you should use the same, or at least as close as possible to, the main speakers. I've tried much smaller speakers as presence speakers before and it just sounded wrong and didn't gel particularly well.

I'd rather not bother than not do it properly.

Since you mention 'presence' speakers (not 'height' speakers ~ even though it's virtually the same thing) I assume you have a Yamaha receiver? Only Yamaha with their DSP processing technology offer 'presence' effects. They've been doing this for decades, long before the newer competing processing modes came along (Audyssey DSX, DTS Neo:X, Dolby PLIIz). Each of these do it a bit differently even though the principle is the same; to enhance the front soundstage. My first two receivers back in the 90's were both Yamaha and I remember vividly how I enjoyed the larger soundstage that the 'presence' processing brought. But, I also found that it was very source dependent, where some soundtracks didn't benefit from it at all, while others did. At times there could also be a slight artificial feeling to the reverb that would occur. However, I know Yamaha have worked to improve this processing since. Now, with their top models they offer the latest "Cinema DSP HD3" (RX-A3020) which I'm sure must be a strong improvement from what I heard years ago. I've had a few demos of the other processing modes aswell and each of them have their good and bad sides. 

If I had an easy way of installing these kind of effect speakers myself in my new home I would probably do it, so I'd say GO FOR IT! Just be realistic on what to expect; these are not channels that will be fed with discretely encoded info from soundtracks, since it's purely a post-processing mode made to subtly enhance with certain effects. If you can demo each mode in a store, do so! I also agree with David above that using identical speakers (if possible) would be ideal to achieve a believable and convincing soundfield. Naturally that assumes you'd be using smaller satellite speakers all-round.

Pity when an OP does not care to even acknowledge the replies