Lots of companies use SumoLogic https://www.sumologic.com/signup/. The UI is very similar to Splunk. But having used both Splunk and SumoLogic, I personally think that Sumo is superior in many ways.
1. It requires very little hacking and setup to work (cough ELK cough Splunk) since Sumo is completely cloud-based. It literally takes 2 minutes to sign up, 5 minutes to download and configure some log collectors, then voila you're ready to send data and search. Also I believe you can tell Sumo Logic to grab logs directly from S3 for example if you're running everything on AWS.
2. SumoLogic is pretty easy to use (it's basically cloud-based grep/awk) and has some really cool features that makes Splunk feel clunky in comparison. Parsing and transposing data for graphing is really simple. Also little things like auto-suggesting sources/hosts while you're typing a query makes the experience much smoother than jumping around tabs copy/pasting shit.
3. If you start to generate a lot of logs, and I mean a metric fuckton of logs from 1000s of servers, Splunk Storm will most definitely not be able to help you. In-house Splunk / ELK clusters will need to be carefully sized (just google ELK sizing).
As software developers, we have enough on our plates that it really pays to use tools that help rather than make you wanna throw up your fists and curse. KISS