Positives:
+ Fluid movement
+ Mods provide unlimited possibilities in weapon customization
+ You can create your own melee weapons in Cetus and secondaries in Fortuna
+ Warframe customization is endless
+ Multiple Warframes allow for many different play styles
+ Certain missions feel fun to play and rewarding (Sorties, Alerts and Arbitrations)
+ Cinematic quests are dynamic and fun too :)
+ Premium currency (Platinum) can be earned via trading or in-game purchase (which is optional, they offer plat discounts on the daily login system)

Negatives:
- Tutorial was good until everything was left up to the player early.
- Game can feel redundant to play depending on the missions you play.
- The market can be confusing for new players to navigate.
- Occasional bugs and glitches
- Host migration is still a problem.
- Space mom doesn't love you :(

Areas of improvement:
- Extended the tutorial, teach the new players about mods (especially upgrading), how the XP and Mastery system works, how the market works, etc.
- Make the market easily accessible for new players, possibly a separate page with recommended weapons for new players as well as items they could purchase with credits.
- Host migration needs to be fixed as there's a chance it can affect the player's earning in the middle of a mission.
- Some bugs are still undiscovered, but keep up the good work with it!

Overall thoughts: Depending on the type of player you are, this game is worth checking out and platinum is an incentive (if you purchase the currency with real money and a 60% or 75% off coupon) if you like to support the company. Same goes with Tennogen cosmetics, but they are optional and have no in-game effects for the player.