The Nexus 5 is large. It's a tiny bit larger than the Nexus 4, though some people have claimed that it actually feels a little smaller.
It's an okay looking phone. The HTC One is much prettier, but the HTC One is also even larger. (The Galaxy S4 is fricken gigantic, and the Google Play edition is also an ugly white.)
The Nexus 5 has a 32 GB version (unlike the Nexus 4) which is... kinda tolerable. The 16GB microSD card in my Nexus One is currently hovering around 2 GB free space left. My 16 GB Nexus 7 recently ran out of space and i had to poke around and clear out some stuff. (The Humble Bundle app apparently leaves old apk files lying around or something, which was part of the problem.) Given that some apps are actually getting up to around the 1 GB size nowdays i'm really not sure how long 32 GB will last me.
If there were a Google Play version of the HTC One Mini, with 32 or 64 GB of storage, a quad core processor and Adreno 320 GPU, and 2GB of RAM then i would be in love, and happily pay $500 or $600 for it.
The other phone that's potentially interesting is the Moto X Developer Edition. It's not quite as powerful as the Nexus 5, but it is a fair bit smaller. Not all the way down to my ideal size range but definitely better. But in order to get the off-contract developer edition with 32 GB storage i'd have to spend $650. And although it's better than other non-Nexus phones it still doesn't have quite the pure Android experience.
And for reference, here's the spreadsheet i've been using to keep track of the various phones that i'm at least moderately interested in:
Google Docs Spreadsheet
The only other even vaguely interesting phone that i know of that's coming out soon is the Moto G, which is rumored to have a release or announce date of November 13th. It's also rumored to be smaller than the Moto X (which is good,) cheaper than the Moto X (which is good,) and have only 8 GB of storage (which is abysmal.)
So my current choices are:
Spend $650 on the Moto X.
Spend $400 on the Nexus 5, and put the ~$200 i'd be "saving" away towards a new cellphone in a year or so if the size really bothers me as much as i worry it might.
Keep waiting for several more months for something else to come out that's better than either of the above options. (Which may or may not happen.)
(And just for reference, i've got about $500-$600 that i've saved up gradually over the last three years, earmarked for getting a new phone.)