I'm in the process of setting up the network at my house. I have a 12U server rack and plan to use Ubiquiti equipment. I'll have a cable modem, UBNT EdgeRouter PoE, UBNT EdgeSwitch, and eventually a server to handle NAS and surveillance camera duties. I'm looking for a solid UPS to sustain the gear through short power outages and offer a soft shut down.

I have looked at the Tripp Lite SMART1500LCDXL, but it seems it doesn't have stellar reviews. I use an APC UPS at work, but was trying to save a little money at home. Does anyone have any solid UPS recommendations in the sub-$300 range?

Use at least a 1200-1500 rated one. One with external 24VDC connection for larger/external batteries for longer run time. If UPS has fan cooled internals even better.

I don't want it to sustain the equipment for long. I want to sustain through the occasional power outage that lasts a minute or two. I want it to provide a soft shut down signal to the server if power is out for an extended time and the battery is reaching critically low levels.

I'm estimating about 300W total power consumption for all of the equipment in the rack. I'd like 5 minutes of up-time or so.

The Tripp Lite UPS I was looking at is 1500VA, expandable, and fan cooled. Amazon seems to give it better reviews than Newegg.

The gotcha I didn't see on Amazon was that the batteries are not user-replaceable. That's almost a deal breaker for me. I liked the price, but not sure about the quality now.

Take a good look at Cyberpower UPS.  (Amazon)CP1000PFCLCD  They make a 1500.

It seems a lot of UPS out there don't react quick enough.  I have one on my TV/Stereo/Cable equipment, and one on my computer.  Recently I was watching down my hallway as some lights were flickering on the other side of the house.  The movie I was watching did not flicker or have any issues at all.

I also find that you never know the batteries are going until that one time you need them.  Put a date on the unit and replace them on a cycle, either every year or two years.  If I let a unit go until the batteries die at a power outage, it usually hammers the UPS too.  I would estimate that on the lower end units, I replace the entire unit 80-90% of the time, rather than replace batteries.

That is what I use on workstations at work.
For my server I have a APC Smart UPS 2200

I use that same tripplite at my house.  It's a bit overkill for what I need but it was on sale.  Desktop, 4 monitors, phone, modem, router, printer.  I get over 10 minutes of run time of If use 2 monitors. About 7 if I  use all 4.

At work all the desktop cube's we use APC1000 Those seem to run about 5 minutes or so with a desktop & 2 monitors, & a phone.

cyberpower is what I use at home. it has the better warranty and easy to service batteries for the larger units.
3 year warranty vs 1 with apc.
I won't buy apc for home use since their warranty sucks. If you have a contract with them they are great.
I don't recall hearing good or bad about triplite.

haven't had any issues with cyberpower if I needed to claim a warranty issue.
All but 1 have been battery issues.
They just happened to go out while I was under warranty and I got free ones.
1 had some issue when it was delievered. they took care of that right away.