Splurge-worthy conveniently-located hotel recommendation?

The Ace Hotel New York is my favorite.  I stay here everytime i'm in NYC.  Period.  They're my permanent digs in NYC.  I stayed at Soho Grand Hotel before making Ace hotel my mainstay.  Great hotel in every respect.

Before shifting to Soho, I stayed at the Hudson Hotel for years.  The W New York Times Square is also solid.

By the way, if you stay at the Ace, you can eat at the famed The Spotted Pig's  kissing cousin located right in the hotel  called  The Breslin. Same proprietor (ken), same vibe/ethos. Rich. Tasty. The eggs w lentils is my fav breaky in NYC.

Another vote for Ace Hotel New York here. A bit hipstery, but very fun! Great bar, there's a Stumptown Coffee Roasters: Ace Hotel in-house, and the rooms are very cute.  Even if I had a hotel booked elsewhere, I'd probably be coming at least once for coffee!

When I think of splurge-worthy and conveniently-located in terms of NY hotels, Crosby Street Hotel comes to mind.  I don't know if there's a spa there, but in terms of location, it really can't be beat, and the space is very nice.  For a spa near Crosby, my fiancee goes to Haven Spa once in a while (though I'm sure you could easily find other spas around there).  If you like tea, Crosby does an afternoon tea and apparently, their weekend brunch is pretty good, too.

I love the The Ritz-Carlton New York Central Park at Central Park. It exudes New York in a way that no other place does for me. C'mon, how can you beat that view?!

Hotel Giraffe is another nice one. Here's a case where "boutique" hotel doesn't mean cramped or cheap. It means beautiful retreat from the chaos that is New York City. Enough ammentities to make it homey and convenient (I'm talking great coffee and breakfast), but so much that you'd be able to stay in your room all day. But why would you want to? You're in NYC for Pete's sake!

Four Seasons Hotel Great Exuma on East 57th puts you in smack dab in the middle of Manhattan. My wife loves it because of the close proximity to shopping in 5th Ave. Everybody wins.

Mandarin Oriental is the epitome of luxury hotels. If money was no object, this is where I would stay every time I visited New York. In fact, I'd live here. Perfectly appointed rooms, flawless service.

W New York - Union Square is another good one. Right near Craft and Union Square Café and has chic amenities.

Trump SoHo Hotel is great but I also love The Carlyle which epitomizes New York glamour, and I die for the Bemelmans Bar!

My go-to is The Pod Hotel on East 51st Street. It's close to a few subway stations and very reasonably priced with a cool vibe.

Try the Ace Hotel New York in midtown.

My wife and I really like the Trump International Hotel & Tower. Great location, great staff, great views. Expensive but worth every penny.

Mandarin Oriental has the nicest spa in the city. Always ranks as one of tops in the world. Although it's kind of small and pricey... typical NYC i guess. The hotel has a cool lounge in the lobby which is like 40th floor and overlooks Central Park South. Even if you don't stay there, it has a nice view and worth a stop if you're near Columbus Circle.

I swear Mandarin Oriental has the best spa and I concur with what Andrew said about it. The second best spa is at the Trump SoHo Hotel, but the service at The Mandarin is bar none.