Is there anything specific about them you wish to know? Generally speaking they're a very nice, well built, medium format/35mm enlarger. They tend to leak a bit of light around the negative carrier but I haven't found it a problem. As far as I'm aware they're still being made so parts are plentiful although so far the only parts I've needed are lamps, glassless carriers and some AN glass.
I had an LPL 6700 for a while, good solid piece of kit, the only slight criticism I would have is that the lamphouse is a little small, therefore runs a little hotter than I would like, sometimes causing negatives in glassless carriers to pop (go out of focus). As ever, this problem is worse with recently-processed film (I think due to the higher water content).
I used a colour LPL 7700 for about 8 years and it was excellent.
The best thing you can have as an accessory is the fine focus attachment. It sits on the RHS of the enlarger and is a critical focusing aid for precise grain focusing.
You can also use the wall mount bracket system designed for the original LPL 4x5 enlarger to wall mount the 7700. You only have to make one modification to the wall mount system, which is to drill one hole near the top of the main bracket. I did this and it was as near to perfection as one can get in that format size enlarger.
Yes there are light leaks from the head, I taped matt black paper around most of the head to virtually eliminate the major leaks, but you will not totally eliminate leaks. The light leaks still around were not detrimental to colour work that I was doing at the time of ownership.
I was recommended the LPL7700 with a colour head by RK Photographic when I set up my first darkroom in 1987. I still have it, so that was a good recommendation! It's not the brightest enlarger around, but it's very solidly built and the focus and height controls are smooth and easily adjusted. I never bothered with the fine focus control - it's an expensive accessory and the standard large knob is adequate if you have a reasonably steady hand. I'd recommend the A_N glass insert if you use the glass neg carrier. Nova sell them I think. Light leaks have not been a significant issue for me, but the filter illumination on the colour head is - there are three bulbs in there, and one is more than enough - in fact I added a switch to mine so I can turn them off.
I use a 7700 and find it works well. The light leaks around the carrier tend to vary with which carrier you have; I find the universal carrier fits quite well. I haven't got the fine-focusing aid, but can imagine that it would be a very nice addition.
All the best with whatever you choose.
The destination is important, but so is the journey