I've been going to Jaco for a number of years, and have stayed at several of the upscale properties, but Diamante Del Sol is the best by far!
First, the property itself is in great shape. It is new, and the finishes in the condos are great. The pool is great, too, and of course, it is right on the beach. The surfing directly in front of the beach is for people a little bit more advanced than me, so we had to walk 10-15 minutes south to catch more forgiving waves. In addition, Jaco get can pretty rowdy at night. This spot is close enough to all the rowdiness, but is still set back enough that you can chill out if you don't want to take in the night life. I had two minor issues with the property - There was no area for storage of surfboards, so every night we had to bring surfboard up to the seventh floor and store them on the balcony (as opposed to leaving the surfboards near the pool area with security as I had done at other spots). Second, the beds were a bit lumpy.
The daystar staff, who managed the property, were EXCELLENT. Tatty is the primary contact person. She is responsive via email and telephone, and answers questions directly. She also gives good recommendations for activities and restaurants. More importantly, if there are concerns, she (and the rest of the staff) address the concerns immediately, and resolve the issues - I have had to make multiple calls at other spots to get small issues fixed -- (i.e. no hot water), but at Diamante Del Sol, the minor hiccups were addressed immediately by Tatty and her staff.
Finally, the price was excellent for the condo. Daystar was also very fair in pricing other services. For example, Daystar arranged the shuttle from the airport to the property at a cost of $100 -- this is $50 cheaper than the management company I used for the shuttle last year. Likewise, Daystar offered a fair price for the Jaco Canopy Tour (zip line), which was intense. I highly recommend this zip line instead of the Los Suenos zip line. The Jaco Canopy Tour provided the best views of town from the mountain, the zip lines were faster moving and higher up (which added to the fear/adrenaline factor),and it is closer to town than the Los Suenos zip line.
All in all, my vacation was fantastic, due to the condo and the management team. I will stay there again!