I have a new 60CSx I've been using for a few days. I use it for hiking/backpacking and skiing. Before I purchased I emailed Garmin to ask if it would support 512MB SD cards. Their response:
Thank you for contacting Garmin International,
Yes, it will support the 512 mb sd cards. However, there is a map set limit.
Right now it is 1025. It should be 2025 after a firmware update is released
by our engineers in the near future.
This is actually my second CSx, the first gave me an error message and would not let me load maps onto the included 64MB card and it would not recognize at all a 128MB card I installed. Garmin tech support was responsive and my dealer (internet purchase from .gpsnow (4x4Books) has great customer service. They allowed me to purchase another and send the first back for a credit to my card when they got it, which they've done as promised. I had also purchased a 60CS from them last year and they are great people to do business with.
I really like the CSx for it's ability to track in forests (NW Washington State). It keeps a solid lock whereas the 60CS is intermittent. The icons are a matter of taste, I like the new ones. Never used the alarm clock on the CS so don't miss it on the CSx. The CSx also has a problem with it's calculation/readings for Total Ascent and Total Descent. It only reads about 50% of the true number (if you ascend 3,000 feet the altimeter tells you you're 3,000 feet higher but your Total Ascent is only 1,500 feet, same for descent). I've talked to Garmin and they've recognized the problem and told me a Firmware update is in the works to fix this.
I liked the CS and I think the CSx is a much better unit because of the improved sensitivity and the use of memory cards. Even with the problems I've had I'm still satisfied because of Garmins responsiveness and the great service at .gpsnow (4x4Books). Haven't really checked battery life but a pair of alkaline AA's last for a 3 hour roundtrip drive and a full day of skiing in the cold and I'm good with that.
All in all, I like the CSx and am happy with my purchase and have every expectation that Garmin will issue software fixes as problems are identified.