The biggest con is the price, the one with the integrated gps is nearly $1000. But I notice that its nowhere near the top-top of the cost curve. You can buy it with or without the gps so that's good in that you only buy what you want and will use and can afford.
The transducer seems to be more fragile than standard. I personally know four (3 50's and 1 50/200) people who've broken theirs...now all four of these guys are on the water more than normal so I dunno if its the design or the amount of use these heads. I drive a jet so this would never do so I switched to an airmar thru-hull transducer so it only sticks down around 5mm. Generally, the positioning of the unit is such that its oriented with the screen raised facing the user. Due to that, water goes into the memory stick slots in the rain. I don't really baby mine, when the boat is in motion I use it....but when I stop, if its raining, I "dab" it off and slap on the cover. Once my cartridge stopped working and I probed all around in the slot to clean it and then all was ok again...I use the cover since.
You can buy navionics or hotmaps for the X15 that give you detailed contours, channels which are really amazingly accurate. They cost as well but they hold a ton of information right on the screen. I use the heck out of the shallow water alarm feature which is quite loud enough (set it wide open) to let me know when its too shallow. I have this set on 2ft so what it really does when it goes off is tell me to turn back toward where I think the channel is. Generally my unit "gives up" at around .9 feet and when the unit "loses the bottom" because its too shallow, I have to get back into 3-4 feet before it can regain it. For me this sometimes means I'm driving around with the depth flashing like a busted VCR...
The details and quality of the screen are great like I said earlier. I can "see" different bait types and can instantly see a cloud of butterbean shad so I know not to throw onto it. I can see my sinkers off the back rod-holders. I really can tell the diff between 4-7 inch shad and 8-14 inch shad. I think that the number one purchasing variable for me is the resolution because of this performance and I'll never buy a unit with less than what I have.
I've used some GPS's that cost ten times what the X15's GPS part does and I'll say that its is a TON of value for the money. The gps is really, really solid. The "trail" feature lays down a line on the screen that you can follow to get home. Stay on that line and even if the vis is bad, you're only gonna be worried about hitting somebody else or a floater, its very nice safety feature.
oh well, nuf rambling. Here's the link to the user manual:
http://www.lowrance.com/Manuals/default.asp
my uit is the lcx 15 mt...jfo