I'm in the market and here are my thoughts. Like you, money isn't a factor. I'm far from rich, but my GPS keeps me out of trouble and is an import part of my riding, so I'm going to get the best. Easier said than done.
I had a Garmin Zumo 665 for a few years. It was TERRIBLE. XM had very poor reception. Bluetooth connection was terrible, and often takes 20 minutes into the ride before it gets a proper connection. Usually I will start out receiving XM or MP3s with a very faint, crackly mono signal instead of stereo- think 60's AM radio. Routing was bad. It loved to take me on loops for no reason, but when I needed to do a loop or go up then backtrack, it would see that as inefficient and bypass those sections. Bad for rally bonuses where I have to turn up a road, get the bonus, then ride back to the main road. I've missed several bonuses because I wasn't paying attention when it did this to me. I think it was just a bad unit, and I HOPE so...explanation below.
I needed a replacement. I looked into the 590, but I see no reason to pay a premium price for a GPS with FEWER features than my 665 had. No XM radio? Weather maps are via a phone connection, which goes against my phone's data plan...plus I have to pay extra for the apps? And all of these services only work where I have a good cell connection, which means they don't work around my home area of New England, except in cities.
Next option. I have heard good things about the Garmin 2797 with 7" screen. Several riders have successfully waterproofed the unit, and it has many similarities to the 590 but at a much lower price. One downfall is no bluetooth connection to my headset, but I could fix that with a Sena dongle. I ordered from Amazon and it looked nice. I tried it a couple days, then when I saw it seemed good, I went to order the pay apps (same ones the 590 uses) and try them. Well surprise, I couldn't buy them because of a problem with how Garmin communicates with Google Play! I kept getting an error. Several phone calls to Garmin resulted in the following explanations: First call: The problem is with Google. Garmin hasn't heard of this problem before. OK, next stop- Google. They assured me the problem wasn't on their end; the error was because Garmin couldn't process the transaction. OK, back to Garmin. Again, the problem isn't with Garmin, it's Google. I got an attitude from the CSR because how dare I question Garmin's reliability. He was downright rude. I wasn't satisfied with that answer, so I called again another day. This time I got the truth- Garmin is aware of the problem, and hasn't found a solution. They are working on one, and as soon as they have one, it will be available in an upcoming update. Really? They are selling GPSs with known problems, making the apps useless? They couldn't give me even a rough estimate how long that would be, so I sent the GPS back. I'm just glad I didn't spend the money on the 590 just to find this out!
So at this point I'm left with buying another 665 and hoping it works better than my first one ever did.
If you are considering the 590, go into Google Play and look at the 1-star rating comments. LOTS of them talking about how the apps don't work.